Interpretive Summary: Potato populations of numerous wild species grow naturally throughout Latin America to the southwest USA. We would like to be able to use the genes in these wild plants for potato improvement, but how can we predict which populations will be most useful. Frost resistance was used as an example to test the usefulness of plant classifications, weather and geographic information in predicting where the most frost hardy plants might be found. Frost hardiness associated well with taxonomic classification. Locations with average minimum temperatures below 3 celcius were more likely to have frost tolerant plants. However, it was hard to find simple and consistent indicators to predict the most frost hardy populations. This work shows that weather and geographic data has some value in predicting the populations that have a certain useful traits in common. These sorts of predictions could make it more efficient to screen populations traits useful for potato breeding.

Technical Abstract:
Frost tolerance in wild potato was analyzed in relation to taxonomic, geographic and ecological factors. We had screening data for 1646 samples from 87 species that had been collected in 12 countries in the Americas. There was a strong association of frost tolerance with species and to a lesser extent with taxonomic series. There is significant geographic clustering of wild potatoes with similar levels of average fros tolerance. Areas with a high level of frost tolerance are the central and southern Peruvian Andes, the lowlands of Argentina and adjacent areas, and a small area in the central Chilean Andes. There is a greater chance of finding wild potatoes with high levels of frost tolerance in areas with an average minimum temperature below 3C than there is in warmer areas. However, temperature is only a weak predictor of frost tolerance because with temperature data alone, the occurrence of frost tolerance in eastern Argentina/Uruguay is not predicted, while falsely predicting it to occur i the southwestern United States. Because many wild potato species occur over small areas, taxonomic, ecological, and geographical factors are easily confounded, and these factors should be analyzed simultaneously to interpret patterns in the distribution of traits.